Multi-millionaire Daily Express owner, Richard Desmond, is suing Credit Suisse claiming the bank mis-sold him a complex derivative, saying the £50m product was “incomprehensible” and left him with an “inappropriately large exposure”.

In legal papers filed with the High Court in London, Mr Desmond claims the 2007 deal, which was arranged by hedge fund GLG, has left him owing at least £20m. As part of his claim, he is asking for the deal to be declared void, or a sum of money equal to the cost of unwinding the transaction.

Mr Desmond, who states in the filing a net worth of £200m, claims he had little understanding of the highly-complex product sold to him that comprised derivatives linked a GLG fund of hedge funds and a zero interest bond.

“It was incomprehensible except to an expert in complex derivative transactions,” according to the legal papers filed by Mr Desmond.

The papers state: “The complexity of the transaction involved structural, credit, market and performance risks that would not have been evident to Mr Desmond.”

The complaint is similar to those that led the Financial Services Authority to investigate the sale of interest rate hedging products to small and medium-sized businesses.

In June, the FSA announced it had reached a compensation deal with Britain’s largest lenders that could see them pay out hundreds of millions and possible several billions of pounds to businesses mis-sold interest rate swaps.

Like Mr Desmond, small businessmen have claimed banks sold them derivative products despite knowing they had little or no understanding of the risks they were taking.

Barclays, Lloyds Banking Group, HSBC and Royal Bank of Scotland have all signed up the FSA compensation process along with several smaller lenders.

Mis-selling victims have complained that the banks did not warn them of the risk should interest rates fall that has left some with costs in the hundreds of thousands and even millions of pounds that they claim they were never warned about.

Despite the deal, many victims are still considering legal actions, saying the terms of the agreement are weighed in favour of the banks.

Mr Desmond claimed in his legal filing that the risks contained in the product he was sold were “impossible to model properly without, at the very least, both significant expertise and full knowledge of the assets constituting the underlying exposure”.

In the case, Mr Desmond is claiming Credit Suisse made a series of misrepresentations as well as breaches of conduct of business rules and common law.

Credit Suisse declined to comment, but is expected to file its defence by September 14.